*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
body{
    background-image: url(blue.jpg);
}
.ab{
    width: 225px;
    height: 50px;
    margin-top: 20px;
    margin-left: 20px;
}
.son{
    opacity: 0;
    height: 400px;
    width: 600px;
    background-color: white;
    margin: auto;
}
.son1{
    width: 600px;
    height: 50px;
    background-color: rgb(204, 204, 204);
}
.a1{
    text-align: center;
    
}
span{
    float: right;
    margin-right: 15px;
}
.b1{
    height: 40px;
}
font{
    margin-top: 40px;
    margin-left: 20px;
}
.c1{
    margin-top: 5px;
    width: 560px;
    height: 150px;
    margin-left: 20px;
}
button{
    width: 80px;
    height: 25px;
}
.a2{
    margin-top: 50px;
    text-align: center;
}

li{
    list-style: none;
    opacity: 0;
    height: 100px;
    width: 800px;
    background-color: white;
    margin-left: 20px;
    margin-top: 15px;
}
b{
    display: none;
}
li:hover b{
    display: block;
    float: right;
}